Short Cracks and Fatigue Life of Materials and Structures

In a design of machines and structures in the transport, energy production, machinery etc. it is necessary to evaluate their fatigue life in order to secure their integrity and safety. Failure is most frequently caused by repeated loading without apparent shape changes. Fatigue crack is initiated and its growth leads to fracture. Application of fracture mechanics allowed describing the growth of long fatigue cracks; however, the damage in the early stages has not been yet assessed. Only the integral Coffin-Manson law could be applied.
Systematic study of the mechanism of the fatigue damage in crystalline materials in the Institute of Physics of Materials ASCR in Brno yielded unique findings about the early stages of fatigue damage - initiation and short crack growth. The period of short crack growth often determines the fatigue life of materials and structures. Adopting high-resolution techniques like atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) the mechanisms of crack initiation was clarified. Detailed measurement of the kinetics of fatigue cracks a short crack law was discovered and this allowed to interpret the Coffin-Manson law. The results yield the methods for more precise prediction of fatigue life based on the new principles which lead to higher safety and reliability of industrial products.

CONTACT PERSON:

Prof. RNDr. Jaroslav Polák, DrSc. Dr.h.c.
phone: (+420) 532 290 366
e-mail: polak@ipm.cz
URL: http://www.ipm.cz/group/people.php?group=18&id=30
More details on the project: http://www.ipm.cz/group/index.php?group=18